Alarm tag

ABSTRACT

An alarm tag is provided having two parts, one of which has a pin attached thereto and extending through the part and into locking engagement with the other part. One part has means for activating an alarm device, the alarm device being either in the other part or an external alarm which interacts with the tag through an alarm field. Further, one part has a contact element operatively related to the other part such that disturbing the pin causes the contact to activate the alarm when the parts are separated.

The invention relates to an alarm tag comprising two parts one of whichis provided with a pin attached to said one part to be located on oneside of a product with the pin extending through the product intolocking engagement with the other part located on the opposite aide ofthe product, said one part having means for activating an alarm devicein said one part.

Existing alarm tags are of one or the other of two types. Either thealarm device is located in the alarm tag so that an alarm will beemitted from the alarm tag at theft of the protected product, or meansin the alarm tag affect an external alarm device so that an alarm isemitted externally at theft. In both cases said one part has acompletely passive element and comprises a head on the pin, mostfrequently of plastics, the only purpose of which is to maintain thealarm tag mechanically on the product. In both cases there aredeficiencies regarding the securily against theft to be afforded by thealarm tag. Thus, it is possible to remove the alarm tag from theprotected product by cutting off the pin or by crushing the plastichead, and if this is done no alarm will be given unless either the pinis withdrawn from the alarm tag or the alarm tag is carried into or outof an external field. It is thus possible to remove the alarm tag andthen walk out carrying the product from the area protected against theftwithout an alarm being given.

The purpose of the invention is to provide an alarm tag which improvesthe security against unauthorized removal from the product to beprotected against theft by means of the alarm tag of the kind referredto above according to the invention comprises two parts, one of which isprovided with a pin attached to the one part to be located on one sideof a product with the pin extending through the product into lockingarrangement with the other part located on the opposite side of theproduct, the one part having means for activating an alarm device in theone part, characterized in that the one part comprises a bistablecontact element operatively related to an electronic control circuit forthe alarm device or a second alarm device, the contact element normallybeing in one stable position in which the alarm device is silent, butbeing constructed to be switched via the pin to the other stableposition in order to activate the alarm device at the attempt toseparate the two parts of the alarm tag.

In order to explain the invention in more detail reference is made tothe accompanying drawing which discloses an illustrative embodiment andwherein

FIG. 1 is a side view of an alarm tag attached to a product which isshown fragmentarily in cross section, and

FIG. 2 is an enlarged cross sectional view of that part of the alarm tagwhich comprises a pin and a head.

In FIG. 1 there is disclosed an alarm tag which comprises a first part10 containing means for initiating alarm from an alarm device whicheither is built into this part or consists of an external alarm device.The alarm is initiated when the alarm tag is carried out from a definedarea in a department store or a shop due to the fact that the alarm tagthen, at the exit from said area, will leave of an electromagnetic orelectrostatic field maintained in said area, or it; carried through sucha field maintained between bows located one at each side of the exitpassage. This part of the alarm tag can be of any existing knownconstruction. Part 10 is applied to one side of a product 11. The alarmtag also comprises a second part 12 consisting of a pin 13 with a head14 said head being applied to the opposite side of product 11 with thepin extending through the product and being attached to part 10. Theattachment is such that the parts cannot be moved apart for removal ofthe alarm tag from the product unless the attachment is operatedmagnetically or mechanically in a special device at the site where theproduct is to be paid, according to a well-known technique applied inconnection with alarm tags.

The invention is based on the knowledge that each attempt to move thetwo parts of the alarm tag apart or to cut off the pin by means of acutter or the like which is inserted between the parts causes deformingforces on the parts. This is utilized according to the invention inorder to emit an alarm from the alarm tag when such deforming forces acton the alarm tag. Instead of being constructed in a known manner as aplastic head the only purpose of which is to maintain in co-operationwith part 10 and pin 13 the alarm tag on the product, head 10 containsaccording to the invention an auxiliary alarm device in addition to thealarm device provided in part 10 or externally, said auxiliary alarmdevice being constructed to be activated as soon as deforming forcesoccur in part 12.

Part 12 is shown in detail in FIG. 2 and as can be seen head 14comprises a bottom plate 15 which has for example circular shape. Saidplate preferably is made of plastics of such kind that the plate isimpact resistant and elastically deformable and also can be fused. Asuitable material is for example polycarbonate. The plate has adownwardly extending peripheral rim 16 which stiffens the plate at theperiphery, and a central bulge 17 in which the pin in attached at a head18 formed on the pin. A cylindrical cover 19 is fused to plate 15 andincludes a circuit board 20 with a battery 21 and an electronic circuit22 located on said board. Contact springs 23 and 24 maintain electricconnection between the electronic circuit and the battery, respectively,and a sound membrane 25. This electronic alarm device can be constructedaccording to principles which are well known in connection withminiature electronic alarm devices and therefore will not be describedin further detail.

A conductive bistable spring washer 26 of metal is located in the spacedefined between circuit board 20 and plate 15, and is attached at acentral opening therein to the bulge 17 by the edge portion around theopening being received in a circular circumferential groove 24 in bulge17. The spring washer functions as a contact clement for switching theelectronic alarm circuit on and off and normally is in one stableposition shown by solid lines, in which the spring washer in archeddownwards and engages at the periphery thereof the upper surface ofplate 15. When the spring washer is in this position the electroniccircuit is de-energized and the alarm device accordingly is passive.Should plate 15 be deformed am can happen by the pin 13 being exposed toaxial tension or by the pin being tilted this will cause the springwasher to snap to the other stable position thereof which is shown bydot and dash lines in FIG. 2. In this position the spring washer isarched upwards in order to engage at the periphery thereof the lowerside of the circuit board 20 which has conductive contact surface 28 forclosing the electronic circuit when the spring washer engages saidcontact surfaces. Then, the alarm device will activate the soundmembrane 25 being induced to oscillate and to emit sound at a suitablefrequency. In the cover 14 slots 29 are provided to "let out" the sound.Inside the cover there may be provided a resonance chamber foramplification of the generated sound.

If the alarm device has been activated it can be shut off by the springwasher being brought to snap back to the position shown by solid lines,but such resetting should of course be possible only in a deviceprovided especially for that purpose by actuation of the spring washer.

The alarm device which in the illustrative embodiment is mounted in head19 is an auxiliary alarm which will be activated as soon as plate 15 isdeformed when somebody tries to remove the alarm tag from the protectedproduct by manipulating the alarm tag. The alarm which sounds whensomebody tries to carry away the product with the alarm tag attachedthereto is emitted from part 10 or from an external alarm device andwill be initiated in a known manner in co-operation with the externalelectromagnetic of electrostatic field. However, it is possible withinthe scope of the invention to have said latter alarm device activatedalso via the bistable contact element and in that case the auxiliaryalarm device can be dispensed with.

As would be easily understood the electronic alarm circuit can beconstructed in many different ways within the scope of the inventiveconcept. It would also be understood that the contact element need notbe a bistable element but can be constructed to trigger an electroniccircuit which keeps the alarm device activated after triggering. In thedisclosed embodiment alarm will be given when an electric circuit isclosed but it is also possible but less advantageous with regard to thepower supply to have the spring washer keep an electric circuit closedwhen the alarm device is silent, alarm being given when said electriccircuits is opened by the spring washer being switched.

I claim:
 1. Alarm tag for a product comprising:a first part to belocated on one side of the product; a pin attached to the first part,the pin extendible through the product when the first part is located onsaid one side of the product; a second part to be located on theopposite side of the product for locking engagement with the pin of thefirst part; means providing locking engagement between the pin and thesecond part; an alarm device in said first part, the alarm device beingelectronically activated; a power source for said alarm device in saidfirst part; an electronic control circuit in said first part forcontrolling interconnection of the power source and the alarm device; aconductive first contact element integrally connected with theelectronic control circuit; and a conductive second contact elementwherein the second contact element is a bistable contact element in thefirst part, said bistable contact element having a first stable positionwhich is the normal position thereof and in which the bistable contactelement is separated from the first contact element, the electronicallycontrolling interconnection thereby being interrupted and the alarmdevice being silent, and said bistable contact element having a secondstable position in which the bistable contact element engages the firstcontact element, the electronically controlling interconnection therebybeing closed and the alarm device being activated, the pin beingoperatively connected with the bistable contact element to switchmomentarily the bistable element from the normal first stable positionto the second stable position thereof in order to activate the alarmdevice at attempt to separate the first and second parts of the alarmtag when in locking engagement with each other.
 2. Alarm tag accordingto claim 1 wherein the bistable contact element comprises a bistablespring washer.
 3. Alarm tag according to claim 1 wherein the bistablecontact element is arranged to be switched to the second stable positionvia the attachment of the pin.
 4. Alarm tag according to claim 1 whereinthe first part forms a resiliently deformable wall, and wherein the pinand the bistable contact element are operatively connected with saidwall.
 5. Alarm tag according to claim 4 wherein the deformable wallforms a bulge and wherein the pin is attached to the bulge.
 6. Alarm tagaccording to claims 2 or 5 wherein said spring washer forms an aperturetherein, and wherein the bulge of the wall forms an annular groove, theedge portion of the spring washer around said aperture being received insaid annular groove.
 7. Alarm tag according to claim 4, wherein thefirst part forms a space receiving the alarm device, the resilientlydeformable wall forming an outside wall of said space.
 8. Alarm tagaccording to claim 7 further including a circuit board inserted into thespace, the electronic control circuit being included in the circuitboard, and contacts on said circuit board for co-operation with thebistable contact element located between the circuit board and theresiliently deformable wall.
 9. Alarm tag according to claim 1 whereinthe electronic control circuit is constructed to be triggered to thesecond stable position of the contact element for continued activationof the alarm device.